This invention relates generally to a ring oscillator in which oscillation frequency is relatively independent of supply voltage.
The conventional ring oscillator comprises an odd number of inverter stages serially connected in a ring. In a conventional CMOS transistor ring oscillator, each stage comprises a p-channel transistor and an n-channel transistor pair serially connected between first and second voltage potentials, typically a positive supply voltage and ground. The common terminal of the transistors is the output of the stage and is connected to the gates of the succeeding transistor pair. Capacitive means shunts the output terminal to ground.
This circuit configuration makes the frequency of the oscillator dependent not only on the number of stages in the ring, but also on the supply voltage, V.sub.CC, for the circuit. As V.sub.CC increases, the frequency of oscillation increases; conversely as V.sub.CC decreases, the frequency of oscillation decreases.